Although Amazon is a great business, it's a terrible stock. The reason is that its stock price is sky high. Compare Amazon's key statistics with those of Wal-Mart. Compare the "Valuation Measures" of the two, and you'll see two quite different stories.
Although the two businesses may seem quite different - notably by Wal-Mart being primarily a brick-and-mortar and Amazon being online - I believe there are more similarities than differences: both are retailers that operate on a massive scale, with highly efficient distribution, and sell to customers at the lowest possible price. And of course, Wal-Mart even sells online, with delivery to home or pickup at the nearest store.
Investors are taking on faith that Amazon's growth in revenue will eventually turn into growth in profits. The author of the linked article seems to believe it, and suggests that those of us who are skeptical just don't get it. However, he admits in the article:
Part of this problem comes from the limited visibility into the dynamics of its business finances. Why doesn't Amazon break out more detail in its financial reporting to help the external world understand all these intricacies? How many subscribers to Amazon Prime, how many Kindles have sold, what's the net income from different lines of business, how much of its asset base investment is for fulfillment centers versus technology infrastructure for AWS?
There may be solid business reasons why Amazon doesn't provide that, but from an investment point of view, a stock with a high valuation whose financials can't be fully understood is the very model of "speculation", as defined by Benjamin Graham, the dean of value investors. Those who invest in Amazon may eventually be rewarded, but the stock market has legions of less-speculative investment opportunities that offer a far better risk/reward ratio. There's no reason for any "intelligent investor" to be involved.
[Disclosure: I have no position in either Amazon or Wal-Mart]